AS160 Associates with the Na+, K+-ATPase and Mediates the Adenosine Monophosphate-stimulated Protein Kinase-dependent Regulation of Sodium Pump Surface Expression

The Na+, K+-ATPase is the major active transport protein found in the plasma membranes of most epithelial cell types. The regulation of Na+, K+-ATPase activity involves a variety of mechanisms, including regulated endocytosis and recycling. Our efforts to identify novel Na+, K+-ATPase binding partners revealed a direct association between the Na+, K+-ATPase and AS160, a Rab-GTPase-activating protein. In COS cells, coexpression of AS160 and Na+, K+-ATPase led to the intracellular retention of the sodium pump. We find that AS160 interacts with the large cytoplasmic NP domain of the alpha-subunit of the Na+, K+-ATPase. Inhibition of the activity of the adenosine monophosphate-stimulated protein kinase ( AMPK) in Madin-Darby canine kidney cells through treatment with Compound C induces Na+, K+-ATPase endocytosis. This effect of Compound C is prevented through the short hairpin RNA-mediated knockdown of AS160, demonstrating that AMPK and AS160 participate in a common pathway to modulate the cell surface expression of the Na+, K+-ATPase.